Methods of forming multiple phase light modulators

• US 5,312,513 A
• Filed: 04/03/1992
• Issued: 05/17/1994
• Est. Priority Date: 04/03/1992
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Boysel, R. Mark, Florence, James M.
• Primary Examiner(s): Powell, William A.
• Application Number:
  US07/862,933
• Time in Patent Office: 774 Days
• Field of Search: 156/630, 156/634, 156/650, 156/652, 156/656, 156/659.1, 156/664, 156/901, 156/665, 156/53, 359/223, 359/291, 359/846, 359/212
• US Class Current: 216/24
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G03H 1/08 Synthesising holograms, i.e. holograms synthesized from objects or objects from hologramsusing electric digital computers G06F; G06T
• CPC Class Codes: G03H 1/0841 Encoding method mapping the synthesized field into a restricted set of values representative of the modulator parameters, e.g. detour phase coding
• CPC Class Codes: G03H 1/2294 Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 2001/0066 for wavefront matching wherein the hologram is arranged to convert a predetermined wavefront into a comprehensive wave, e.g. associative memory recognition using holographic masks G06V10/88
• CPC Class Codes: G03H 2001/085 Kinoform, i.e. phase only encoding wherein the computed field is processed into a distribution of phase differences
• CPC Class Codes: G03H 2001/0858 Cell encoding wherein each computed values is represented by at least two pixels of the modulator, e.g. detour phase coding
• CPC Class Codes: G03H 2223/13 Phase mask
• CPC Class Codes: G03H 2225/24 Having movable pixels, e.g. microelectromechanical systems [MEMS]
• CPC Class Codes: G03H 2225/31 Amplitude only
• CPC Class Codes: G03H 2225/32 Phase only
• CPC Class Codes: G03H 2225/55 Having optical element registered to each pixel
• CPC Class Codes: G03H 2240/41 Binary
• CPC Class Codes: G03H 2240/42 Discrete level
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field

Abstract

A method for multiple phase light modulation, said method comprising providing a pixel (20) having at least two modulating elements (22),(24). The method further comprising addressing said at least two modulating elements (22), (24) whereby light incident on said addressed element undergoes discrete phase changes between addressable states. The method further comprises resolving light from said at least two modulating elements (22), (24), into a response having at least three unique phases. Other devices, systems and methods are also disclosed.

Claims

1. A method for forming a DMD having movable mirror elements for modulating incident light, said method comprising:

a) providing a substrate having addressing circuitry;

b) forming a first mirror metal layer over said substrate, said first mirror metal layer in electrical communication with a first address electrode of said addressing circuitry;

c) forming a first mirror etch stop overlying said first mirror metal layer;

d) patterning said first mirror etch stop whereby said first mirror etch stop overlies a first mirror area;

e) forming a second mirror metal layer over said first mirror metal layer and over said first mirror etch stop;

f) forming a second mirror etch stop overlying said second mirror metal layer;

g) patterning said second mirror etch stop whereby said second mirror etch stop overlies a second mirror area;

h) removing said second mirror metal layer in areas not underlying said patterned second mirror etch stop to form a second mirror element; and

i) removing said first metal mirror layers in areas not underlying said patterned first mirror etch stop of sad second mirror etch stop to form a first mirror element in electrical communication with said first address electrode.

2. The method of claim 1 wherein said second mirror element is in electrical communication with said second address electrode.

3. The method of claim 1 and further comprising the following steps prior to removing said second mirror metal layer.

a) forming a third mirror metal layer, said third mirror metal in electrical communication with a third address electrode of said addressing circuitry;

and

b) forming a third mirror etch stop.

4. The method of claim 1 wherein at least one of said mirror elements is a movable mirror element that is vertically translated in response to an address voltage being placed on its respective address electrode.

5. The method of claim 4 and further comprising the step of forming stops prior to forming said first mirror metal layer whereby the travel of said mirror elements can be controlled.

6. The method of claim 1 wherein at least one of said mirror elements is a movable mirror element that is vertically translated by an odd multiple of one fourth of a selected light wavelength whereby a π

radian phase difference exists between light reflected from said at least one vertically translated reflective element and a non-vertically translated reflective element.

7. The method of claim 1 wherein said mirror elements are aluminum.

8. The method of claim 1, wherein said removing of at least one of said mirror metal layers is by plasma etching.

9. The method of claim 1 wherein said addressing circuitry is binary addressing circuitry.

10. The method of claim 1 wherein said mirror elements are grouped to form macropixels.

11. The method of claim 10 wherein said macropixel is a part of a physical array of like macropixels.

12. The method of claim 10 wherein said physical array is similar to a DRAM.

13. The method of claim 9 wherein said physical array is similar to an SRAM.

14. The method of claim 1 and further comprising the following steps prior to forming said first mirror metal layer.

a) forming a metal layer over said substrate;

b) patterning said metal layer to provide base pads for hinge support vias;

c) forming stops whereby the travel of said mirror elements can be controlled;

d) forming a first spacer layer over said substrate &

said metal layer;

e) patterning said first spacer layer to form hinge support vias;

f) forming hinge metal over said first spacer layer and over said hinge support vias,

g) patterning said hinge metal to form mirror hinges;

h) forming beam metal over said hinge metal; and

i) patterning said beam metal to form beams.

15. The method of claim 14 wherein said beams are aluminum.

16. The method of claim 14 wherein said beams are titanium.

17. A method for forming a DMD having movable mirror elements for modulating incident light, said method comprising:

providing a substrate having binary addressing circuitry;

forming a metal layer over said substrate;

patterning said metal layer to provide base pads for hinge support vias;

forming stops whereby the travel of said movable mirror elements can be controlled;

forming a first spacer layer;

patterning said first spacer layer to form hinge support via cavities in said first spacer layer;

forming hinge metal over said first spacer layer and over said hinge support via cavities;

forming buried hinge etch stop over said hinge metal;

pattern said buried hinge etch stop;

forming beam metal over said hinge metal and said buried hinge etch stop;

forming a beam metal etch stop over said beam metal;

patterning said beam metal etch stop;

removing said beam metal in areas not covered by beam metal etch stop;

removing hinge metal in areas not covered by the buried hinge etch stop;

forming a second spacer layer;

patterning said second spacer layer to form mirror support via cavities;

forming a first mirror metal layer;

forming a first mirror etch stop;

patterning said first mirror etch stop whereby said first mirror etch stop overlies a first mirror area;

forming a second mirror metal layer;

forming a second mirror etch stop;

patterning said second mirror etch stop whereby said second mirror etch stop overlies a second mirror area;

removing said second mirror metal layer in areas not underlying said second mirror etch stop;

removing said first metal mirror layers in areas not underlying said first mirror etch stop or said second mirror etch stop; and

removing said first and second spacer layers.

18. A method for forming a DMD having movable mirror elements for modulating incident light, said method comprising:

a) providing a substrate having binary addressing circuitry;

b) forming a first metal layer over said substrate, said first mirror metal layer in electrical communication with a first address electrode of said addressing circuitry;

c) forming a first mirror etch stop over said first mirror metal layer;

d) patterning said first mirror etch stop whereby said first mirror etch stop overlies a first mirror area;

e) forming a second mirror metal layer, said second mirror metal layer in electrical communication with a second address electrode of said addressing circuitry;

f) forming a second mirror etch stop over said second mirror metal layer;

g) patterning said second mirror etch stop whereby said second mirror etch stop overlies a second mirror area;

h) removing by plasma etching said second mirror metal layer in areas not underlying said patterned second mirror etch stop to form a second mirror element; and

i) removing by plasma etching said first mirror layers in areas not underlying said patterned first mirror etch stop or said second mirror etch stop to form a first mirror element in electrical communication with said first address electrode wherein said first mirror element is a movable mirror element that is vertically translated in response to an address voltage being placed on said first address electrode.

19. The method of claim 18 wherein said second mirror element is in electrical communication with said second address electrode.

20. The method of claim 18 wherein said mirror elements are grouped to form macropixels.